Windows Vista’s System Protection feature can eat up a lot of disk space on your system, and while it’s supposed to return space to you if you need it, if you find yourself running low on space you can free space up manually by doing the following:

1. Start the System utility in Control Panel
2. Allow the UAC prompt
3. Select the System Protection tab
4. Clear the checkmark beside the volume System Protection is enabled on.

Note that this will delete all restore points for that volume, so note that if you do this you won’t be able to restore your system to a previous condition if you need to.